Screw-thread die



July 4, 1950 H. J. HAYCOCK ET AL 2,513,864

SCREW THREAD DIES Filed March 10, 1947 FIG-.2. FIG. 3.

9M: fla/nr/o/ #a cov ima e/$64 0 6M 6M Patented July 4, 1950 Harold James Haycock, Solihull, and Harold George Carmichael Wilson, Stratford-on-Avon,

England Application March 10, 1947, Serial No. 733,628 In Great Britain February 21,1946

2 Claims.

The present invention relates to screw thread dies especially high precision dies such as are used in forming or cutting screw threads on cylindrical parts.

As is well known, dies of the kind referred to and as at present used are provided with a number of lateral grooves or flutes extending the whole length of the operative or thread forming part of the die, the number of such flutes varying according to the size of the die. Such dies may or may not be chamfered at the leading end to form a lead.

The provision of these flutes, whether they be straight or of spiral form, is that the screw thread cutting and forming part of the die, is left as a series of isolated lands extending the effective length of the die, which fact materially weakens the die to torsional stresses and, moreover, renders the die difficult to gauge or measure for high precision work, calling for a tolerance on the work of the order of one thousandth of an inch.

tion 1 aforesaid is instrumental in directing the swarf away from the corresponding cutting edge 9 to the peripheral edge of the die and also instrumental in directing the swarf in front of the die as the latter advances along the work being threaded thereby.

The remaining central portion of the full thread form 3, Figure 2, forms stabilising means for the die on the work.

In order to enable the die to be reversed and so present fresh cutting edges the other face of the die as shown in Figures 2 and 3 may be formed The presence of the flute also reduces the stability of the die on the work on which it is forming a thread.

Referring to the drawings:

Figure 1 is a face view of a die according to the present invention.

Figure 2 is a side view thereof in the direction of the arrow A in Figure 1, and

Figure 3 is a section on the line 3-3 of Figure 1.

Referring to the drawings, the die I is provided with the usual transverse peripheral locating slots 2 and is provided with a complete thread 3 interrupted by gashes 4, which gashes extend through the lead 5 and into, but not through, the complete thread 3.

The gashes 4 are formed in the complete thread 3 by forming recesses 6 in the face of the die in such a manner that the axes of the recesses are inclined to the face of the die and that they break through into the thread 3 removing portions of the latter to form, in effect, gashes 4 therein.

The recesses 6 are preferably produced by means of an end mill or the like cutting tool applied with its axis inclined to the face of the die. The curved side portions 1 of each recess 6 form with the corresponding remaining part 8 of the with a similar series of recesses I I to form swarf directing surfaces I2 and cutting edges l3, which latter series of recesses are preferably staggered with respect to the beforementioned recesses 6, as shown, so that the die body is not unduly weakened by the formation of the recesses.

The accompanying drawings show the present invention applied to a relatively small sized die, larger sizes thereof would preferably feature a greater number of recesses 6, H and corresponding cutting edges 9, [3.

We claim:

1. Improvements connected with screw thread dies wherein the die has an uninterrupted complete thread formed therein which is adapted to stabilise the die on the work being threaded, a lead to said thread formed by chamfering the first few convolutions thereof, axially inclined recesses formed in the face of said die so as to break into the thread lead and complete thread to form gashes therein said gashes extending from the lead into but not through the complete thread, backed-off cutting edges formed by said recesses and the adjacent remaining part of the lead and first few full formed threads, and flat portions inclined to the face of the die formed by running out said gashes to the peripheral edge of said die adapted together with the sides of said recesses to direct the swarf away from said cutting edges and in front of the die as the latter is a thread portion of full form in said threaded bore adapted to stabilize the die on work bein threaded thereby; cutting edges formed by said gashes and the adjacent remaining parts of the lead and first few threads of full form; curved I sides to said recesses inclined to the face-of the die and extending from the cutting edges: to the peripheral edge of the die; fiat portions forming bottoms to said recesses inclined with respect to the face of the die and running out to the said face at the peripheral edge of the'die, said inclined flat portions and curved sides of said recesses being adapted to direct the swarf away from said cutting edges and in front of the die as the latter is advanced along the work being threaded.

HAROLD JAMES HAYCOCK.

HAROLD GEORGE CARMICHAEL WILSON.

REFERENCES CITED The following references are of record in the file of this patent: I

UNITED STATES PATENTS Number Name Date 561,913 Paquette June 9, 1896 689,555 Mann Dec. 24, 1901 1,165,989 McIntyre Dec. 28, 1915 1,524,235 Germain Jan. 27, 1925 FOREIGN PATENTS Number Country Date Switzerland Oct 14, 1903 

